No crashers allowed

Opera version 11.01, running on Windows 7 (32-bit version), crashed minutes ago when navigating a perfectly ordinary Joomla! site of mine. I allowed the crash report to be submitted, but there seemed to be no current known cause:

The rest of the page tells you what to do (keep software up-to-date, run anti-virus scans etc) if you are experiencing frequent crashers! What?